Membrane assembly of touch sensitive pads for electronic equipment has typically been performed in a labor intensive manner by positioning a first component on a hard surface, removing a protective liner covering the adhesive on the top surface of the first component and positioning a second component on top of the first component and then manually applying pressure with a roller in an attempt to roll out all of the air bubbles that have been trapped between the first and second components that have been layered on one another. The manual placement also produces an undesirable amount of variation between the position of the second component superimposed with respect to the first component. Defects due to improper placement and the inclusion of unremovable air bubbles or other debris trapped in between the two layers causes a high rate of defective parts, which must be scraped, greatly increasing the overall cost of the acceptable completed assemblies.
Typically, a touch sensitive pad includes at least three layers which are laminated to one another. The first layer generally includes a substrate which may be rigid or flexible in nature supporting exposed electrically conductive areas separated from one another by non-conductive material areas that are partially or totally subsequently covered with an appropriate adhesive for laminating the second layer to the first layer. The second layer typically includes a resiliently flexible non-conductive material having open areas alignable with the conductive material areas of the first layer, and a suitable adhesive for receiving the third layer. The third layer is laminated in assembly with the previously laminated first and second layers against the adhesive of the second layer and typically is formed of a flexible sheet material having a conductive material at least in areas facing the conductive material of the first layer but separated by a fluid chamber formed by the open areas through the second layer. In operation, the operator's pressure on the third component surface pushes the electrically conductive surface of the third component layer into contact with the electrically conductive surface of the first component layer to complete a circuit between the first component layer and the third component layer, or to complete an electrical circuit between two separated electrically conductive portions formed in the first component layer by the bridging contact of the electrically conductive material in the third component layer.
A sheet laminating machine for feeding laminated sets to a press roller is disclosed in U.S. Pat. No. 3,671,363. Alignment between components of the multiple sheets to be laminated is accomplished by a stop engaging the leading edges of the sheets to be laminated as the sheets are fed toward a pressure roller. The stop is moved by the sheets in response to the feeding movement of the sheets themselves toward the roller. The stop is moved downwardly by the roller to a point below the plane of the sheets virtually simultaneously with the commencement of the pressure applying operation by the pressure roller onto the sheets. As soon as the stop passes beyond the trailing edges of the sheets being laminated, the stop returns to its normal position and is ready for engagement by and guiding of the next following sets of sheets to be laminated.
A method and apparatus for stacking a plurality of laminate layers to form a composite board is disclosed in U.S. Pat. No. 4,506,442. The apparatus stacks a plurality of laminate layers in registered, superimposed relation to enable the layers to be joined to form a composite board. The apparatus includes a table having a surface on which a plurality of laminate layers can be successively stacked in aligned, superimposed relation on pins slidably received in respective apertures in the table. The pins rest on support members which are carried on a lower support table mounted beneath the surface of the table in which the laminate layers are stacked. The lower support table is raised relative to the stack of laminate layers after successive laminate layers have been placed on the pins so that a given projection of the pins from the laminate layers will be obtained.
An alignment-registration tool for fabricating multi-layer electronic packages is disclosed in U.S. Pat. No. 5,048,178. The first layer of the package is brought into proximity to an optical system which is adapted for imaging a surface of the layer. The optical system images features on the surface of the first layer and generates targets around selected ones of the features. The next layer of the circuit package is brought into proximity to the optical system. The next layer is moved, by translation and rotation, until selected features of the layer coincide with the target generated through the optical system. This next layer is then placed atop the previous layer. Finally, the layers are laminated to form the multi-layer micro electronic circuit package.
A method of fabricating multi-layer board is disclosed in U.S. Pat. No. 4,991,285. The multi-layer board is fabricated by plating up conductive posts on a non-conductive layer. The tops of the posts are planarized, resulting in sharp corners. The posts are aligned with a template which has an aperture above each post and a second non-conductive layer is placed between the top of the post and the bottom of the template. The two layers are laminated together by compressing the second layer between the first layer and the template, and the posts punch through the second layer. Conductive traces may then be etched or deposited between the post tops and the process may be repeated as many times as desired.
None of the devices previously known provides an apparatus for sheet-to-sheet lamination of membrane assemblies in a manner to eliminate or greatly reduce the inclusion of undesirable air entrapment, wrinkles or bubbles.